Here’s a book on artificial intelligence that the author made available online in 2002. He recently went through and updated each of the 40+ chapters with links to wikipedia. It’s meant to compete with the standard text in the field: Artificial Intelligence: A Modern Approach.

The Artificial Intelligence Wikipedia-based Free Textbook is
a collection of forty-plus module/chapter webpages with links
from each module into related technical articles on Wikipedia,
the free on-line encyclopedia. As Wikipedia grows and solidifies,
the free AI textbook also grows and solidifies. Included are
sample AI source-code programs, such as a JavaScript AI tutorial.